Gas discharge display apparatus utilizing hollow cathode light sources

ABSTRACT

Gas discharge display apparatus comprising a plurality of hollow cathodes and associated anodes enclosed in a gastight envelope with an ionizable gas. The hollow cathodes are arranged in a predetermined pattern in order that ignition of gas discharges in the hollow portions of selected cathodes provides the desired display. The anodes are proximate to the hollow portions of the cathodes and the hollow portions have a depth such that only cathode glow discharges substantially confined thereto may occur. Thus, sputtered cathodic material is substantially confined to the interiors of the hollow portions. The anodes are disposed adjacent the hollow portions of the cathodes but exterior thereof for minimizing interelectrode short-circuiting due to sputtering. An individual display light source having a hollow cathode member and a transparent member sealed to the cathode member enclosing the hollow portion thereof and an associated anode with an ionizable gas is also disclosed.

United States Patent 51 3,662,2 1 4 Lustig [451 May 9, 1972 [54] GASDISCHARGE DISPLAY Primary Examiner-Roy Lake APPARATUS UTILIZING HOLLOWAssistant Examiner-Lawrence J. Dahl CATHODE LIGHT SOURCES [72] Inventor:Claude D. Lustig, Lexington, Mass. [57] ABSTRACT [73] Assignee: SperryRand Corporation, Great Neck, Gas discharge display apparatus comprisinga plurality of hol- N.Y. low cathodes and associated anodes enclosed ina gastight en- Filed p 13 1970 velope with an ionizable gas. The hollowcathodes are ar- Appl. No.: 27,608

ranged in a predetermined pattern in order that ignition of gasdischarges in the hollow portions of selected cathodes provides thedesired display. The anodes are proximate to the hollow portions of thecathodes and the hollow portions have a depth such that only cathodeglow discharges substantially confined thereto may occur. Thus,sputtered cathodic material is substantially confined to the interiorsof the hollow portions. The anodes are disposed adjacent the hollowportions of the cathodes but exterior thereof for minimizinginterelectrode short-circuiting due to sputtering. An individual displaylight source having a hollow cathode member and a transparent membersealed to the cathode member enclosing the hollow portion thereof and anassociated anode with an ionizable gas is also disclosed.

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ATTORNEY BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention pertains to visual display apparatus particularly ofthe gas discharge variety.

2. Description of the Prior Art Visual displays are known that utilizelight emitting semiconductor elements such as gallium arsenide diodesarranged in matrix configurations. Selective energization of theelements of the matrix produces visual displays of desired symbols.Apparatus of this character tends to be expensive because of the highcost of the semiconductor elements utilized. Additionally, presentlyavailable light emitting semiconductor elements are not capable ofgenerating high intensity light outputs thus limiting the environmentsin which such displays may effectively be used.

Gas discharge display devices are known that require A.C. excitationacross the electrodes of the elements comprising the display to igniteand sustain electrical discharges through the gas. Such displays tend toradiate r.f. interference signals possibly obstructing the operation ofelectronic equipment in the vicinity thereof. Displays utilizing A.C.excitation require complex addressing and energizing circuits topreferentially ignite discharges at selected elements of the device inorder to form desired symbols. Such apparatus tends to be excessivelyexpensive. Additionally, A.C. excited displays often require excessivelylarge energizing voltages hence aggravating the problems previouslydiscussed.

D.C. excited gas discharge displays are known that remedy several of thedeficiencies of the A.C. excited displays discussed. For example, D.C.devices do not radiate r.f. interference signals, do not require complexaddressing circuits and do not require excessively large energizingvoltages as do the A.C. devices. D.C. excited displays often utilizeorthogonally oriented sets of conductors immersed in an ionizable gas orindividually energizable gas cells. Applying a suitable D.C. potentialbetween selected conductors of the device ignites gas discharges in thegas cells thereof. Because of metal sputtering that often occurs at thecathode electrodes of such devices, apparatus of this character is oftensubject to failure and degradation of operating characteristics becauseof cathode erosion, shorting between electrodes and obscuration of thetransparent viewing envelope because of deposition of cathodic metalthereon. In order to obtain a bright display, high currents must beutilized between the electrodes of the elements hence aggravating thesputtering problem and further shortening the operating life of thedevice. Cathodes with large surface areas may be utilized to reduce theerosion effects of sputtering. This, however, results in poorly definedglow discharges that spread over the increased cathode surfaces henceproviding a display with inadequate resolution.

Although several of the prior art devices have cathode elemerits withhollow portions, the glow is often not confined to the hollow portionsthus aggravating the problems discussed above. In addition, these priordevices often have the anode electrodes protruding into the hollowportions of the cathodes thus precipitating interelectrodeshort-circuiting due to sputtered cathodic metal. The cathode glowdischarges provided by these prior devices are often viewed throughnarrow apertures thus decreasing the light output efficiency thereof.

Devices of the type described above may be utilized, for example, forlarge panel computer operated information displays, or smalleralphanumeric readout indicators or for bright outdoor display panelssuch as may be utilized in commercial advertising. The disadvantagesdiscussed above such as inadequate resolution, short life, insufficientlight output, obstructed glow discharges and high cost tend to limit theusefulness of such devices for applications of the type described.

SUMMARY OF THE INVENTION The present invention provides a D.C. excitedgas discharge display comprising a plurality of hollow cathodes arrangedin a predetermined pattern. The hollow portions or holes in the cathodesand the associated anodes are enclosed in a gas-tight envelope with anionizable gas. Energization of selected cathodes and anodes by suitableD.C. potentials applied therebetween ignites gas discharges in the holesof the selected cathodes thereby providing the desired display.

Since the gas discharges are confined substantially to the holes in thecathodes because of the geometry of the hollow cathode light cellsutilized, the resolution of the device is limited only by the dimensionsof the hollow cathodes that may practically be constructed. Since thearea utilized to generate the gas discharge at each cathode may extendinto the interior surface of the cathode hole, a relatively largecathodic surface area is provided for each gas discharge cell. Hencerelatively high currents can be utilized in a cell providing a highintensity output without excessively large current densities at thecathode. Thus the sputtering of the cathodic metal is reduced. Theundesirable effects of sputtering are further reduced because thesputtered cathodic material should be symmetrically redistributed withinthe interior of the cathode hole. Hence, the operating life of displaysembodied in accordance with the present invention should be increasedand the problems associated therewith decreased with respect to theprior configurations previously discussed.

Since the structure of the present invention is relatively uncomplicatedand the device may be addressed and energized utilizing simple D.C.potentials, the cost of the present apparatus is reduced with respect tothe prior devices.

Since the present invention is energized with D.C. potentials, theanodes thereof may be of a small and unobtrusive construction thus notobstructing the glow discharges from view as in prior configurations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspectiveview, partially in section, of a display device constructed inaccordance with the present invention utilizing individual addressing ofthe elements of the display and including a block schematic diagram ofthe addressing circuits.

FIG. 2 is an exploded perspective view, partially in section, of anotherembodiment of the present invention utilizing individual addressing ofthe elements of the display and including a block schematic diagram ofthe addressing circuits.

FIG. 3 is an exploded perspective view of a display device constructedin accordance with the present invention utilizing coordinate selectaddressing of the elements of the display and including a blockschematic diagram of the addressing circuits.

FIG. 4 is an exploded perspective view of another embodiment of thepresent invention utilizing coordinate select addressing of the elementsof the display and including a block schematic diagram of the addressingcircuits.

FIG. 5 is an exploded perspective view, partially in section,illustrating a modification to the device of FIGS. 1-4 providing amulticolored display capability.

FIG. 6 is a side elevational view, partially in section, of anindividual hollow cathode light source constructed in accordance withthe present invention, and

FIG. 7 is a waveform diagram illustrating potentials useful inenergizing the elements of the displays illustrated in FIGS. 3 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, anembodiment of the present invention is illustrated and will be describedin terms of an alphanumeric or symbol readout indicator 10 of a typethat may be utilized, for example, in electronic calculators.

A dielectric member 1 1, which may be composed of a suitable materialsuch as glass or ceramic, has a plurality of holes formed therein in apredetermined pattern. For the purposes of explanation, a 5 X 7rectangular array of holes is disclosed, a typical one of which is hole12. It can be appreciated that other patterns of holes may be utilized,such as the conventional numeric or alphanumeric patterns, depending onthe purpose for which the indicator is intended. In addition, a hole 13and holes 14 are included to provide a decimal point and a comma,respectively.

A hollow cathode 16 is sealed in the hole 12 and a plurality ofidentical hollow cathodes are sealed in the remaining holes in themember 11 respectively. The hollow cathode 16 may comprise a metal rodwith an axial hole 17 formed therein. An electrical conductor 20connects the hollow cathode 16 to addressing circuits 21 and a pluralityof identical electrical conductors connect the remaining cathodesrespectively thereto for reasons to be explained.

A source of potential 22 provides D.C. voltages to the addressingcircuits 21 in a manner and for reasons to be discussed.

A transparent dielectric member 23, which may be composed of glass, issealed to the dielectric member 11 with a shim 24 disposed therebetween.The sealed together members 11 and 23, spaced apart by the shim 24, forma gas-tight envelope enclosing the hole 17 of the cathode l6 and theholes in the remaining cathodes respectively. It may be appreciated thatthe dielectric member 11 may be formed with the shim 24 as an integralpart thereof or alternatively the shim may be formed as part of thetransparent dielectric member 23. Any convenient method known in thevacuum tube art may be utilized to hermetically seal together themembers 11 and 23. It is to be understood that the cathode 16 ishermetically sealed in the hole 12 and the remaining cathodes aresimilarly sealed in the remaining respective holes in the member 11.

A metal anode 25 disposed on the surface 26 of the member 23 ispositioned adjacent the holes of the cathodes and spaced therefrom. Theanode 25 may be a transparent metal film, such as tin-oxide, depositedon the surface 26. It may be appreciated that other metallic coatings,as well as a fine metal mesh, may equivalently be utilized. A conductivetab 27 is included to make electrical contact from the exterior of thegastight envelope to the anode film 25. The tab 27 is connected to theaddressing circuits 21 via an electrical conductor 30 for reasons to beexplained.

It may be appreciated that one of the cathodes, such as cathode 31, maybe utilized as the full-tube for the gas-tight envelope formed by themembers 11 and 23. The fill-tube 31 may be a metal tube through whichthe envelope may be evacuated. The envelope may then be filled with anionizable gas such as neon, argon or Penning mixture (99.5 percent neon,0.5 percent argon) to a reduced pressure such as 75 torr. The tube 31may then be sealed off by any conventional method known in the art ofvacuum tube construction. Alternatively, a conventional fill tube may beutilized for these puroses.

p The operation of the display device may be appreciated from anunderstanding of the operation of an individual hollow cathode lightsource thereof. A positive DC. potential of sufficient amplitude appliedbetween the anode 25 and the cathode 16 ignites an electrical dischargein the hole 17. This potential is often referred to as the ignition orfiring potential, A potential of sufficiently smaller amplitude thanthat of the ignition potential applied therebetween extinguishes anydischarge sustained in the hole 17. This potential is referred to as theextinction potential.

The operating potentials for a hollow cathode gas discharge cell aredependent on the ionizable gas utilized and on its pressure as well ason the geometry and spacing of the electrodes. Utilizing cathode holesof approximately 0.04 inch diameter and 0.06 inch depth and an anode tocathode spacing of approximately 0.025 of an inch in a Penning mixture(99.5 percent neon 0.5 percent argon) at a pressure of 75 torr, properoperation has been obtained with ignition and extinction potentials ofapproximately 160 and volts respectively. It is to be appreciated thatthe operating parameters given are not critical and that departurestherefrom may be made in practicing the invention.

In operation, ground potential may be applied to the anode 25 by thesource of potential 22 via the addressing circuits 21 and the lead 30.Cathodes selected by the addressing circuits 21 may have --l60 voltsapplied thereto from the source of potential 22. Non-selected cathodesmay be grounded by means of the addressing circuits 21. Thus, electricaldischarges are ignited in the holes of the selected cathodes hencedisplaying a desired symbol or character. For example, applying theignition potential to the cathodes 32 and the extinction potential tothe remaining cathodes causes the numeral 4 to be displayed.

It may be appreciated that the addressing circuits 21 may compriseconventional logic circuits for applying the ignition and extinctionpotentials provided by the source 22 selectively to cathodes of thedisplay 10 in response to data inputs at a terminal 33. Hence a largevariety of characters and symbols may selectively be displayed by the 5X 7 matrix of hollow cathodes as well as an associated decimal point andcomma provided by the cathodes sealed in the holes 13 and 14respectively.

As previously discussed, the display device 10 may be employed as analphanumeric readout indicator of the type utilized in electroniccalculators. it may be appreciated that substantiaily the same designmay be used in outdoor display panels by suitably increasing thedimensions of the component parts of the device and by utilizing alarger matrix of cathodes. The cathode rods may be further lengthenedand the holes therein deepened so that high intensity displays may begenerated by large currents drawn through the extended interior surfacearea of the cathodes. Adequate cooling for such high intensity displaysmay conveniently be obtained by convective or forced air flow over thecathode rods extending from the back of the member 11. Electricalcontact to the individual cathodes is conveniently made at these exposedportions of the cathode rods.

It may be appreciated that the top surface of the cathode rods may bemounted flush with the top surface of the member 11. It may further beappreciated that the top surface of the rods may alternatively berecessed into the holes in the member 11 to reduce the etfect of anyresidual sputtering of cathodic material onto adjacent electrodes.

The device 10 has been described in terms of the holes in the member 11being formed therethrough with the cathode rods sealed therein andexposed at the back surface 34. It may be appreciated that the holes inthe member 11 need not extend completely therethrough and that hollowcylinders inserted into the holes may be utilized as the cathodicelectrodes. With such an arrangement, the member 11 may com prise atransparent dielectric block through the back surface 34 of which thecathodic discharges may be viewed. The transparent dielectric member 23may then be replaced by a metallic member sealed to the dielectricmember 11 to form the gas-tight envelope, the metallic memberfunctioning as the anode of the device.

It may further be appreciated that the cathodes may be formed in theholes of the member 11 by conventional plating techniques.

Referring now to FIG. 2, in which like reference numerals refer to likecomponents with respect to FIG. 1, another embodiment 40 of the presentinvention is illustrated which may be utilized for the same purposes asthose described with respect to the embodiment 10. The device 40,however, incorporates design features that render the manufacturingthereof more economical than that of the device 10.

An electrically conductive cathode member 41, which may be composed ofany suitable metal, has a plurality of holes formed therein in apredetermined pattern. The holes may be arranged in accordance with anyof the patterns discussed with respect to FIG. 1 and are each extendingonly partially through the member 41. The interior surface of each holeforms the hollow cathode electrode of a light cell of the display 40 ina manner to be explained An electrical conductor 42 connects theconductive cathode member 41 to the addressing circuits 21 for reasonsto be discussed.

A transparent dielectric member 43, which may be composed of glass, issealed to the cathode member 41 with a shim 44 disposed therebetween.The sealed together members 41 and 43, spaced apart by the shim 44, forma gas-tight envelope enclosing the holes in the cathode member 41 in amanner similar to that described with respect to FIG. 1. The shim 44 maybe formed as an integral part of either member 41 or 43 in the mannerdiscussed with respect to FIG. 1. The gas-tight envelope thus formed maybe evacuated and filled with an ionizable gas, such as neon, argon orPenning mixture at reduced pressure, in any convenient manner known inthe art of vacuum tube construction.

The anode electrodes for the device 40 are comprised of electricalconductors 45 disposed on the surface 46 of the member 43 internal tothe gas-tight envelope. The anodes 45 may comprise transparent metalfilm strips, such as tin-oxide, deposited on the surface 46. It may beappreciated that unobtrusive anode strips of other metals notnecessarily transparent, as well as other anode constructions, mayequivalently be utilized. The anode strips are arranged adjacent therespective holes of the cathode member 41, each strip and its associatedhole forming a hollow cathode gas discharge light source of the display40 in a manner to be described. Electrically conductive tabs 47,connected to the respective anode strips 45, are included to makeelectrical contact thereto from the exterior of the gas-tight envelope.The tabs 47 are connected, via respective leads 50, to the addressingcircuits 21 for reasons to be explained.

It is understood that the strips 45 must be electrically insulated fromthe conductive cathode member 41. This may achieved in any convenientmanner known to the art. For example, the shim 44 may be composed of adielectric material and may be positioned between the anode strips 45and the cathode member 41 thus preventing electrical contacttherebetween.

The operation of the display device 40 is similar to that described withrespect to the device of FIG. 1. Ground potential may be applied to thecathode member 41 by a source of potential 48 via the addressingcircuits 21 and the lead 42. Anode strips 45, selected by the addressingcircuits 21, may have the positive ignition potential applied theretofrom the source of potential 48. Non-selected anode strips may begrounded by means of the addressing circuits 21. Electrical gasdischarges are thereby ignited preferentially in the cathode holesadjacent the energized anode strips. Thus it may be appreciated thatdesired symbols or characters are displayed by the device 10 in responseto data inputs at the terminal 33 in a manner similar to that describedwith respect to FIG. 1.

It should be understood that an anode strip 45 must be disposed adjacentonly those cathode holes to be energized thereby. The pattern of anodestrips on the surface 45 must be arranged so that no strip is adjacent ahole with which it is not associated. This is required so thatdischarges are not ignited in holes that are not associated withenergized strips thus preserving the fidelity of the display patterns.As an alternative, electrically insulating material 51, such as glassfrit, may be utilized to cover the respective surfaces of the stripsexcept at those portions thereof that are adjacent the associated holes.

It may be appreciated that more than one cathode hole may be associatedwith each anode strip if discharges in these holes are always ignitedand extinguished concurrently with respect to each other.

It may further be appreciated that the display apparatus 40 may beemployed for uses similar to those discussed with respect to FIG. 1 andmay be more economical to manufacture than the device 10 because of itsless complex constructional design. The operating parameters for thedevice 40 may differ from those of the device 10, previously discussedwith respect to FIG. 1, because of the constructional differencestherebetween.

It may be understood that although the cathode member 41 has beendescribed in terms of holes that are formed partially therethrough, theapparatus 40 may be constructed with holes formed completely through themember 41. A transparent member (not shown) may then be utilized to sealthe back surface 52 of the member 41 to complete the gas-tight envelope.The gas discharges may then be viewed through the transparent member.

It may further be appreciated that light intensity from the devicesillustrated in FIGS. 1 and 2 may be varied over wide ranges by adjustingthe operating currents thereof to accommodate different viewingenvironments.

Referring now to FIG. 3, in which like reference numerals refer to likeelements with respect to FIG. 1, another embodiment 60 of the presentinvention is illustrated particularly suitable for use as a large paneldisplay. The apparatus 60 may, for example, be operatively associatedwith a computer or used for outdoor commercial advertising. The elementsof the display 60 are energized by a coordinate selection technique tobe described.

A dielectric member 61, which may be composed of a suitable materialsuch as glass or ceramic, has a plurality of holes formed therein whichare arranged in a matrix 62 of rows and columns. For purposes ofexplanation a 5 X 5 matrix of holes is disclosed. It is understood,however, that in a practical display, thousands or tens of thousands ofholes may be utilized in matrix configuration.

A plurality of hollow cathodes 63 similar to those described withrespect to FIG. 1 are sealed in the respective holes of the member 61 ina manner similar to that previously discussed with respect to FIG. 1.The cathodes of each row of the matrix 62 are connected together byelectrical row conductors 64-68 respectively, which in turn areconnected to addressing circuits 71 for reasons to be explained.

A source of potential 72 provides D.C. voltages to the addressingcircuits 71 in a manner and for reasons to be discussed.

A transparent dielectric member 73, which may be composed of glass, issealed to the dielectric member 61 with a shim 74 disposed therebetween.The sealed together members 61 and 73, spaced apart by the shim 74, forma gas-tight envelope enclosing the holes in the hollow cathodes 63 in amanner similar to that described with respect to FIG. 1. The shim 74 maybe formed as an integral part of either member 61 or 73 in the mannerdiscussed with respect to FIG. 1. The gas-tight envelope thus formed maybe evacuated and filled with an ionizable gas as previously describedwith respect to FIG. 1. It may be appreciated that one of the cathodes,for example cathode 75, may be utilized as the fill tube for thegastight envelope in the manner previously explained.

The anode electrodes for the device 60 are comprised of electricalconductors 76-80 disposed on the surface 83 of the member 73 internal tothe gas-tight envelope. The anodes 76-80 may comprise respectivetransparent metal film strips, such as tin-oxide, disposed on thesurface 83. It may be appreciated that anode strips of other metals, aswell as other anode constructions such as fine wires, may equivalentlybe utilized. The anode strips 76-80 are arranged in columns adjacent theholes of the columns of cathodes of the matrix 62 respectively.Electrically conductive tabs 84, connected to the respective anodestrips 76-80, are included to make electrical contact thereto from theexterior of the gas-tight envelope. The tabs 84 are connected, viarespective leads 8589, to the addressing circuits 71 for reasons to beexplained.

The operation of an individual hollow cathode light source of thedisplay 60 is similar to that described with respect to an individualcell of the device 10 of FIG. 1. Ignition and extinction potentials arerequired for the reasons given with respect to FIG. I and, in addition,a voltage intermediate in amplitude thereto is required to sustaindischarges that have been ignited. This voltage may be referred to asthe sustaining potential. It may be appreciated that the sustainingpotential is insufficient to ignite a discharge in a cell and that adischarge ignited in a cell is sustained by application of thesustaining potential thereacross.

The operating potentials for a hollow cathode gas discharge cell aredependent on the ionizable gas utilized and on its pressure as well ason the geometry and spacing of the electrodes. Utilizing cathode holesof approximately 0.062 inch diameter and 0.2 inch depth and an anode tocathode spacing of approximately 0.05 inch in a neon atmosphere at apressure of 12 torr, proper operation has been obtained with ignition,sustaining and extinction potentials of 330, 230 and 130 voltsrespectively. It is to be appreciated that these operating parametersare not critical and that departures therefrom may be made in practicingthe invention.

In operation, ground potential may be applied to the row conductors64-68 by the source of potential 72 via the addressing circuits 71. Thesustaining potential of 230 volts may be applied to the anode strips76-80 by the source of potential 72 via the addressing circuits 7] andthe leads 85-89 respectively. Thus it may be appreciated that thesustaining potential of 230 volts is applied across each hollow cathodecell of the matrix 62.

In order to ignite a discharge in a hole of a selected cathode of thematrix 62, the addressing circuits 71 increase the potential applied tothe anode strip associated with the selected cathode and decrease thepotential applied to the row conductor associated therewith so that thepotential across the selected cell is equal to the ignition potential.The increased and decreased potentials are chosen so that the potentialacross the non-selected cells of the matrix 62 remain less than theignition potential. When the increased and decreased potentials areremoved from the selected conductors, the sustaining potential appliedto all of the cells of the matrix 62 sustains the discharge ignited inthe hole of the selected cathode.

In order to extinguish discharge in a hole of a selected cathode of thematrix 62 the addressing circuits 71 decrease the potential applied tothe anode strip associated with the selected cathode and increase thepotential applied to the row conductor associated therewith so that thepotential across the selected cell is equal to the extinction potential.The decreased and increased potentials are chosen so that the potentialacross the non-selected cells of the matrix 62 remain greater than theextinction potential. Hence, only the discharge in the hole of theselected cathode is extinguished.

For example, if it is desired to ignite a discharge in the hole 93 ofthe cathode 92, the sustaining potential of 230 volts applied to theanode strip 76 may be increased by 50 volts to a potential of 280 volts.Simultaneously, the ground potential applied to the row conductor 64 maybe decreased by 50 volts to a potential of 50 volts. Thus a differenceof potential of 330 volts is applied between the anode 76 and thecathode 92 hence igniting a discharge in the hole 93 thereof. It may beappreciated that the cells in the row and column of the matrix 62associated with the cathode 92 have 280 volts applied thereacross whichis insufficient to ignite discharges therein.

As a further example, if it is desired to extinguish a discharge in thehole 93 of the cathode 92, the sustaining potential of 230 volts appliedto the anode strip 76 may be decreased by 50 volts to a potential of 180volts. Simultaneously, the ground potential applied to the rowconductors 64 may be increased to 50 volts. Thus a difference ofpotential of 130 volts is applied between the anode 76 and the cathode92 hence extinguishing any discharge sustained in the hole 93 thereof.It may be appreciated that the cells in the row and column of the matrix62 associated with the cathode 92 have 180 volts applied thereacrosswhich is insufficient to extinguish discharges sustained therein.

It may therefore be appreciated that by appropriate energization of therow conductors 64-68 and the anode strips 76-80, selected cathodes ofthe matrix 62 may be ignited and extinguished thus displaying a desiredinformation pattern on the device 60.

It may further be appreciated that the addressing circuits 71 maycomprise conventional logic circuits for applying the ignition,sustaining and extinction potentials provided by the source 72selectively to the row conductors 64-68 and to the anode strips 76-80 inresponse to data inputs at the terminal 33. Hence a large variety ofdisplay patterns may selectively be generated by the matrix 62 of hollowcathode light cells.

The potentials selectively provided by the addressing circuits 71 areillustrated in FIG. 7. It may be appreciated that it is not necessary tosymmetrically increase and decrease the sustaining voltages ashereinabove explained in order to generate the ignition and extinctionpotentials. An applied voltage scheme difierent from the one specifiedmay be chosen requiring an asymmetrical increase and decrease of thesustaining voltage to generate the ignition and extinction potentials.

It may be appreciated that the display 60 is suitable for applicationsrequiring a high intensity display for the reasons given with respect toFIG. 1.

It is further understood that the transparent member 73 should bedisposed close to the front surface of the dielectric member 61 so thatthe migration of ions and electrons between the various cathodes of thedisplay is prevented. This is necessary to avoid the improper ignitionof discharges in non-selected holes. The top surface of the rods 63 arerecessed into the holes in the member 61 to maintain an anode-cathodespacing appropriate for optimum performance of the device.

The device 60 has been described in terms of the holes in the member 61being formed therethrough with the cathode rods 63 sealed therein andexposed at the back surface of the member 61. It may be appreciated thatthe holes in the member 61 need not extend completely therethrough andthat hollow cylinders inserted into the holes may be utilized as thecathodic electrodes. With such an arrangement, the member 61 maycomprise a transparent dielectric block through the back surface ofwhich the cathodic discharges may be viewed. It may further beappreciated that the cathodes may be formed in the holes of the member61 by conventional plating techniques.

Referring now to FIG. 4, in which like reference numerals refer to likecomponents with respect to FIG. 3, another embodiment of the presentinvention is illustrated which may be utilized for the same purposes asthose described with respect to the embodiment 60. The device 100,however, incorporates a hollow cathode structure 101 that may bemechanically stronger and more economical to manufacture than that ofthe device 60.

The hollow cathode structure 101 comprises a plurality of electricallyconductive cathode members 102-106 having rows of holes formed thereinrespectively. The holes may extend only partially through the members102-106, the interior surface of each hole forming the hollow cathodeelectrode of a light cell in a manner similar to that described withrespect to FIG. 2. The members 102-106 may be composed of any suitablemetal and are aligned with respect to each other so that the respectiverows of holes form columns of holes. It may thus be appreciated that theholes in the cathode members 102-106 form a matrix of rows and columns.For purposes of explanation a 5 X 5 matrix of holes is disclosed.However, it is understood that practical displays may utilize largermatrices as previously explained with respect to FIG. 3. Theelectrically conductive cathode members 102-106 are connected to theaddressing circuits 71 via leads 107-111 respectively for reasonspreviously discussed with respect to FIG. 3. The source of potential 72provides D.C. voltages to the addressing circuits 7] in the manner andfor the reasons explained with respect to FIG. 3.

The cathode members 102-106 include ridges 114 positioned respectivelybetween adjacent holes thereof for reasons to be explained. The cathodemembers 102-106 are sealed together with electrical insulators 115-118disposed respectively therebetween. The top surfaces of the insulators115-118 are in alignment with the top surfaces of the ridges 1 14 forreasons to be clarified.

A transparent dielectric member 121, similar to the member 73 of FIG. 3,is sealed to the cathode structure 101 around the edges thereof forminga gas-tight envelope enclosing the holes in the cathode members 102-106in a manner similar to that described with respect to FIG. 3. Themembers 101 and 121 may be sealed together at the edges by anyconventional means (not shown for clarity) known in the art of vacuumtube construction. The surface 122 of the member 121 is disposedabutting the top surfaces of the ridges 1 14 and the insulators 115-118for reasons to be explained. The gastight envelope formed between themembers 101 and 121 may be evacuated and filled with an ionizable gas,such as neon, argon or Penning mixture at reduced pressure, in anyconvenient manner known to the art of vacuum tube construction.

The anode electrodes 123-127 are disposed and arranged on the surface122 of the member 121 in a manner identical to that described withrespect to the member 73 of FIG. 3. The electrodes 123-127 thereforeform columnar anodes adjacent the respective columns of holes in themember 101 in the manner described with respect to FIG. 3. Electricallyconductive tabs 130, connected to the respective anode strips 123-127,are included to make electrical contact thereto from the exterior of thegas-tight envelope. The tabs 130 are connected to the addressingcircuits 71 in the manner and for the reasons discussed with respect toFIG. 3.

The operation of an individual hollow cathode light source of thedisplay 100 is similar to that described with respect to an individualcell of the device 40 of FIG. 2. The operation of the display device 100where electrical discharges are selectively ignited and extinguished inthe holes of the cathode structure 101 by appropriate energization ofthe leads 107-111 and the anode strips 123-127, thereby displayingdesired information patterns, is identical to the operation of thedevice 60 described with respect to FIG. 3. For example, applying theignition and extinction potentials to the electrically conductivecathode member 102 via the lead 107 and to the anode strip 125selectively ignites and extinguishes electrical discharges in the hole131 respectively.

In order to prevent the improper ignition of discharges in non-selectedholes due to the migration of ions and electrons between cathodes,barriers may be required around each hole of the matrix. The ridges 114and the insulators 115-118, the top surfaces of which abut the surface122 of the member 121, may form the required barriers.

It may be understood that although the cathode structure 101 has beendescribed in terms of holes that are formed partially therethrough, theapparatus 100 may be constructed with holes formed completely throughthe cathode members 102-106. A transparent member (not shown) may thenbe utilized to seal the back surface 132 of the structure 101 tocomplete the gas-tight envelope. The gas discharges may then be viewedthrough the transparent member.

Referring now to FIG. 5, a modification of the devices depicted in FIGS.1-4 is illustrated that provides a multi-colored display capability. Abroken-out portion of a display is shown illustrating the operatingprinciples of the modified embodiment.

Sections 140 and 141 are representative of, for example, portions ofdisplays such as the display 40 of FIG. 2 where the holes in the cathodemembers 142 and 143 are formed completely therethrough. The pattern ofholes in the member 142 may be identical to the pattern of holes in themember 143. The members 142 and 143 are aligned relative to each otherso that corresponding holes therethrough are in axial alignment withrespect to each other. Transparent members 144 and 145 are sealed,respectively, to the members 142 and 143 forming respective gas-tightenvelopes in the manner described with respect to FIG. 2. The gas-tightenvelopes associated with the sections and 141 may be filled withdifferent ionizable gases with respect to each other. For example, theenvelope associated with section 140 may be filled with neon and theenvelope associated with section 141 may be filled with argon in themanner described with respect to FIG. 2

The members 142 and 143 are sealed to the opposite surfaces of atransparent member 146. The member 146 may be utilized to complete thegas-tight envelopes associated with the sections 140 and 141respectively.

Electrical discharges may selectively be ignited and extinguished in thecathode holes of the members 142 and 143 utilizing any of the techniquesdescribed with respect to FIGS. 1-4. For example, an electricaldischarge may be ignited or extinguished in the hole 150 and similarlyan electrical discharge may be ignited or extinguished in the hole 151which is in axial alignment therewith.

Electrical discharges through the neon gas in the gas-tight envelopeassociated with the section 140 emit a red colored light and electricaldischarges through the argon gas in the gas-tight envelope associatedwith the section 141 emit a blue colored light. It may be appreciatedthat because of internal reflections within the holes of the members 142and 143, light emanating from a hole in the member 143 is transmittednot only through the transparent member but also through the transparentmember 146 into the corresponding hole in the member 142 andconsequently through the member 144. Conversely, light emanating from ahole in the member 142 may be viewed through the transparent member 145.Furthermore, because of internal reflections within the holes, colorfidelity is obtained over large viewing angles since light from the rearcells is visible over large angles after reflections at the insidesurfaces of the front cells.

In operation when an electrical discharge is sustained in the hole 150,for example, and there is no electrical discharge in the hole 151, redlight can be viewed through both the members 144 and 145 at the locationof the holes and 151. Conversely, if an electrical discharge in the hole151 and there is no electrical discharge in the hole 150, the color bluemay be viewed at this location of the display. If electrical dischargesare sustained in both the holes 150 and 151, the red and blue lightgenerated respectively therein appears at the location of the holes 150and 151 as a pink color.

It may be appreciated that by appropriate choices of ionizable gases avariety of colors may selectively be displayed by apparatus configuredin accordance with the present invention.

Referring now to FIG. 6, an individual hollow cathode light sourceconstructed in accordance with the present invention is illustrated. Agas-tight envelope is formed by a hollow cathode 161 and a transparentmember 162 hermetically sealed thereto. The transparent member 162 maybe composed of glass. The transparent member 162 may be sealed to thecathode member 161 by any conventional technique known in the art ofvacuum tube construction. An electrically conductive anode 163 isdisposed on the surface of the member 162 internal to the gas-tightenvelope 160. The anode 163 may, for example, be any suitabletransparent metal film deposited on the inner surface of the member 162.The envelope 160 may be evacuated and filled with an ionizable gas at areduced pressure by means of a conventional fill tube 164. Leads 165 and166, connected to the cathode 161 and the anode 163, respectively, maybe utilized for applying suitable potentials to the light source.

In operation the application of suitable ignition and extinctionpotentials between the leads 165 and 166 may selectively ignite orextinguish an electrical discharge within the hole 167, respectively.

A plurality of individual hollow cathode light sources, of the typeillustrated in FIG. 6, may be utilized in combination to form a varietyof display configurations.

It may be appreciated that the display devices described hereinabovewith respect to FIGS. 1-4 incorporate constructional features thatprovide rugged devices which are economical to manufacture.

It may further be appreciated that the devices described with respect toFIGS. 1 and 2 are particularly suited to applications where a reasonablysmall number of hollow cathode light cells are required, for example, inan alphanumeric readout indicator. Since each light cell of the devicesof FIGS. 1 and 2 requires a separate lead for energization thereof, adisplay with a large number of light cells, and consequently a largenumber of leads, may be prohibitively cumbersome.

The display devices illustrated in FIGS. 3 and 4 are particularlysuitable for applications where a large number of light cells arerequired. Such applications occur, for example, in computer controlledinformation display panels and in outdoor commercial advertisingdisplays. Since the cells of the apparatus illustrated in FIGS. 3 and 4are energized by a coordinate selection technique, a smaller number ofleads are required relative to the number of cells in the display.

It may be appreciated that prior art hollow cathode light sources areoften constructed with the anode spaced an extended distance from thecathode hence providing the capability of columnar type dischargesthrough the gas. Such discharges are unsuited to the applicationsdiscussed hereinabove, for which the present invention is designed,because of the exceedingly inferior resolution that such devices wouldprovide and the detrimental sputtering problems precipitated thereby. Inthe present invention the anodes are disposed adjacent the holes of thehollow cathodes in such proximity thereto that columnar discharges areprecluded. Only cathode glow discharges are permitted to occur in thepresent invention. The discharges are confined substantially to theinterior of the holes in the cathodes because of the geometry of thecells utilized hence providing superior display resolution compared tothe prior devices previously discussed.

In addition, the sputtering problems are reduced compared to the priordevices since the sputtered cathodic metal is substantially confined tothe cathode holes and is symmetrically redistributed around the interiorsurfaces thereof. Hence a long-lived bright display is provided sincethe glass viewing plate thereof is not readily obscured by the sputteredcathode metal as in the prior devices. Additionally, the interelectrodeshort-circuiting problem due to sputtered cathode metal is substantiallyreduced, particularly since the anode electrodes are located external tothe cathode holes.

Since in the present invention the entire glow discharges sustainedwithin the cathode holes contribute to the viewed display, in contrastto prior devices where the glow discharges may be viewed through narrowapertures, the light output efficiency of the present device is superiorto that of such prior configurations.

While the invention has been described in its preferred embodiments itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes may be made withinthe purview of the appended claims without departing from the true scopeand spirit of the invention.

I claim:

1. Gas discharge display apparatus comprising cathode means having aplurality of hollow cathode portions arranged in a predeterminedpattern,

anode means spaced from said cathode means and disposed adjacent saidhollow portions but exterior thereof for minimizing interelectrodeshort-circuiting due to sputter- 8,

gastight envelope means enclosing said hollow portions and said anodemeans with an ionizable gas,

said envelope means having a transparent portion for viewing said hollowcathode portions, and

connection means included in said cathode and anode means adapted forconnection to a source of electrical potential to selectively applysuitable potentials between said anode and cathode means for providingelectrical discharges in selected hollow cathode portions, said anodemeans being in such proximity to said hollow portions and said hollowportions having a depth such that only cathode glow dischargessubstantially confined thereto may occur thereby substantially confiningsputtered cathodic material to the interiors of said hollow portions anddefining sharply demarcated glow discharges,

each said hollow cathode portion having side wall surfaces providing theprimary electron emitting surfaces thereof, said side wall surfaceshaving low resistivity and said connecting means associated therewithproviding a high conductance path from said side wall surfaces to saidsource of potential.

2. The apparatus recited in claim 1 in which said potentials comprisepositive potentials at said anode means with respect to said cathodemeans.

3. The apparatus recited in claim 1 in which said cathode meanscomprises a first dielectric member having a plurality of holes arrangedtherein in a predetermined pattern, and

a plurality of electrically conductive hollow cathodes having respectivehollow portions therein,

said cathodes being disposed in said holes in said first dielectricmember respectively.

4. The apparatus recited in claim 3 further including a second membersealed to said first dielectric member thereby forming said envelopemeans.

5. The apparatus recited in claim 4 in which said second membercomprises a transparent dielectric member for viewing said cathodes, and

said anode means comprises a transparent electrically conductive filmdisposed on the surface of said transparent dielectric member internalto said envelope means.

6. The apparatus recited in claim 3 in which said cathodes comprise,respectively, electrically conductive rods having respective axial holesformed therein.

7. The apparatus recited in claim 6 in which said holes in said firstdielectric member extend therethrough, and

said rods are hermetically sealed in said holes whereby portions thereofare exposed to the exterior of said envelope means for making electricalconnection thereto and for efficient cooling thereof. 8. The apparatusrecited in claim 6 further including, a source of positive electricalpotential sufficient to ignite electrical discharges through saidionizable gas, and

addressing means coupling said connection means to said source ofelectrical potential for applying said positive potential to said anodemeans with respect to selected ones of said plurality of rods therebyproducing electrical discharges in selected holes of said rods.

9. The apparatus recited in claim 7 in which one of said rods comprisesthe sealed fill tube for said envelope means.

10. The apparatus recited in claim 1 in which said cathode meanscomprises an electrically conductive cathode member having a pluralityof holes therein arranged in a predetermined pattern, and

said anode means comprises a plurality of electrical conductors disposedadjacent said holes, respectively.

11. The apparatus recited in claim 10 further including a dielectricmember sealed to said cathode member thereby forming said envelopemeans.

12. The apparatus recited in claim 11 in which said dielectric membercomprises a transparent member for viewing said cathode member, and

said electrical conductors comprise respective electrically conductivestn'ps disposed on the surface of said transparent dielectric memberinternal to said envelope means.

13. The apparatus recited in claim 12 in which said strips are coveredalong their respective surfaces with a dielectric material except atthose portions thereof adjacent said holes.

14. The apparatus recited in claim 12 further including a source ofpositive electrical potential sufficient to ignite electrical dischargesthrough said ionizable gas, and

addressing means coupling said connection means to said source ofelectrical potential for applying said positive potential to selectedones of said plurality of strips with respect to said conductive cathodemember thereby producing electrical discharges in selected holes of saidcathode member.

15. The apparatus recited in claim 1 in which said cathode meanscomprises a first dielectric member having a plurality of holes arrangedtherein in a matrix of rows and columns, and

a plurality of electrically conductive hollow cathodes having respectivehollow portions therein,

said cathodes being disposed in said holes in said first dielectricmember respectively. 16. The apparatus recited in claim 15 in which saidanode means comprises a plurality of first electrical conductors eachdisposed adjacent the hollow portions of a respective column of saidcathodes, and

said cathode means includes a plurality of electrical row conductorseach connecting the cathodes of a respective row.

17. The apparatus recited in claim 16 further including a seconddielectric member sealed to said first dielectric member thereby formingsaid envelope means.

18. The apparatus recited in claim 17 in which said second dielectricmember comprises a transparent member for viewing said cathodes, and

said first electrical conductors comprise respective electricallyconductive strips disposed on the surface of said transparent dielectricmember internal to said envelope means.

19. The apparatus recited in claim 16 in which said cathodes comprise,respectively, electrically conductive rods having respective axial holesformed therein.

20. The apparatus recited in claim 19 in which said holes in said firstdielectric member extend therethrough,

said rods are hermetically sealed in said holes whereby portions thereofare exposed to the exterior of said envelope means, and

said plurality of electrical row conductors are connected to saidexposed portions.

21. The apparatus recited in claim 19 further including means forapplying a positive potential to all of said first electrical conductorswith respect to all of said row conductors sufi'icient to sustainelectrical discharges through said ionizable gas, means for increasingthe potential at a selected one of said first electrical conductors andfor decreasing the potential at a selected one of said row conductorsthereby producing a potential therebetween sufficient to ignite anelectrical discharge in the hole associated with the intersection ofsaid selected conductors, and means for decreasing the potential at aselected one of said first electrical conductors and for increasing thepotential at a selected one of said row conductors thereby producing apotential therebetween sufficient to extinguish any electrical dischargesustained in the hole associated with the intersection of said selectedconductors. 22. The apparatus recited in claim 20 in which one of saidrods comprises the sealed fill tube for said envelope means.

23. The apparatus recited in claim 1 in which said cathode meanscomprises a plurality of electrically conductive cathode members eachhaving a row of holes therein, said rows being aligned to form columnsof holes, and

said anode means comprises a plurality of first electrical conductorseach disposed adjacent a respective column of said holes.

24. The apparatus recited in claim 23 in which said cathode members aresealed together with electrical insulator means disposed therebetween.

25. The apparatus recited in claim 24 further including a dielectricmember sealed to said cathode members thereby forming said envelopemeans.

26. The apparatus recited in claim 25 in which said dielectric membercomprises a transparent member for viewing said cathode members, and

said first electrical conductors comprise respective electricallyconductive strips disposed on the surface of said transparent memberinternal to said envelope means.

27. The apparatus recited in claim 26 in which each said cathode memberincludes a ridge between each pair of adjacent holes disposed therein,

said ridges and said electrical insulator means extending to saidsurface of said transparent member internal to said envelope meansthereby forming a barrier around each of said holes. 28. The apparatusrecited in claim 26 further including means for applying a positivepotential to all of said strips with respect to all of said cathodemembers sufficient to sustain electrical discharges through saidionizable gas,

means for increasing the potential at a selected one of said strips andfor decreasing the potential at a selected one of said cathode membersthereby producing a potential between said selected strip and saidselected cathode member sufficient to ignite an electrical discharge inthe hole therein associated with said selected strip, and

means for decreasing the potential at a selected one of said strips andfor increasing the potential at a selected one of said cathode membersthereby producing a potential between said selected strip and saidselected cathode member sufficient to extinguish any electricaldischarge sustained in the hole therein associated with said selectedstrip.

29. Gas discharge display apparatus comprising first cathode meanshaving a plurality of first hollow cathode portions therein having firstand second openings thereinto respectively,

first anode means spaced from said first cathode means and disposedadjacent said first hollow portions,

first gas-tight envelope means enclosing said first hollow portions andsaid first anode means with a first ionizable 8 said first envelopemeans including transparent portions adjacent said first and secondopenings respectively,

second cathode means having a plurality of second hollow cathodeportions therein having third and fourth openings thereintorespectively,

second anode means spaced from said second cathode means and disposedadjacent said second hollow portions,

second gas-tight envelope means enclosing said second hollow portionsand said second anode means with a second ionizable gas,

said second envelope means including transparent portions adjacent saidthird and fourth openings respectively, and connection means included insaid cathode and anode means adapted for connection to a source ofelectrical potential to selectively apply suitable potentials betweensaid anode and cathode means to produce electrical discharges inselected hollow cathode portions,

said first and second cathode means being disposed adjacent each otherwith said first and second hollow portions being aligned whereby lightemanating from said second and fourth openings enters said associatedfourth and second openings respectively after transmission through saidassociated transparent portions disposed therebetween.

30. A gas discharge display element comprising an electricallyconductive hollow cathode having a hollow portion therein,

an electrically conductive anode spaced from said cathode and disposedadjacent said hollow portion,

a transparent member hermetically sealed to said cathode forming agas-tight envelope enclosing said hollow portion and said anode with anionizable gas, and

connection means adapted for connection to a source of electricalpotential to selectively apply a suitable potential between said anodeand cathode to produce an electrical discharge in said hollow portion,

said hollow portion having side wall surfaces providing the primaryelectron emitting surfaces thereof, said side wall surfaces having lowresistivity and said connecting means associated there-with providing ahigh conductance path from said side wall surfaces to said source ofpotential,

31. The apparatus recited in claim 30 in which said anode comprises atransparent electrically conductive film disposed on the surface of saidtransparent member internal to said envelope.

32. The apparatus recited in claim 30 in which said potential comprisesa positive potential at said anode with respect to said cathodesufficient to ignite electrical discharge through said ionizable gas.

33. The apparatus recited in claim 30 in which said anode is in suchproximity to said hollow portion that only cathode glow dischargessubstantially confined to said hollow portion may occur.

1. Gas discharge display apparatus comprising cathode means having aplurality of hollow cathode portions arranged in a predeterminedpattern, anode means spaced from said cathode means and disposedadjacent said hollow portions but exterior thereof for minimizinginterelectrode short-circuiting due to sputtering, gas-tight envelopemeans enclosing said hollow portions and said anode means with anionizable gas, said envelope means having a transparent portion forviewing said hollow cathode portions, and connection means included insaid cathode and anode means adapted for connection to a source ofelectrical potential to selectively apply suitable potentials betweensaid anode and cathode means for providing electrical discharges inselected hollow cathode portions, said anode means being in suchproximity to said hollow portions and said hollow portions having adepth such that only cathode glow discharges substantially confinedthereto may occur thereby substantially confining sputtered cathodicmaterial to the interiors of said hollow portions and defining sharplydemarcated glow discharges, each said hollow cathode portion having sidewall surfaces providing the primary electron emitting surfaces thereof,said side wall surfaces having low resistivity and said connecting meansassociated therewith providing a high conductance path from said sidewall surfaces to said source of potential.
 2. The apparatus recited inclaim 1 in which said potentials comprise positive potentials at saidanode means wIth respect to said cathode means.
 3. The apparatus recitedin claim 1 in which said cathode means comprises a first dielectricmember having a plurality of holes arranged therein in a predeterminedpattern, and a plurality of electrically conductive hollow cathodeshaving respective hollow portions therein, said cathodes being disposedin said holes in said first dielectric member respectively.
 4. Theapparatus recited in claim 3 further including a second member sealed tosaid first dielectric member thereby forming said envelope means.
 5. Theapparatus recited in claim 4 in which said second member comprises atransparent dielectric member for viewing said cathodes, and said anodemeans comprises a transparent electrically conductive film disposed onthe surface of said transparent dielectric member internal to saidenvelope means.
 6. The apparatus recited in claim 3 in which saidcathodes comprise, respectively, electrically conductive rods havingrespective axial holes formed therein.
 7. The apparatus recited in claim6 in which said holes in said first dielectric member extendthere-through, and said rods are hermetically sealed in said holeswhereby portions thereof are exposed to the exterior of said envelopemeans for making electrical connection thereto and for efficient coolingthereof.
 8. The apparatus recited in claim 6 further including, a sourceof positive electrical potential sufficient to ignite electricaldischarges through said ionizable gas, and addressing means couplingsaid connection means to said source of electrical potential forapplying said positive potential to said anode means with respect toselected ones of said plurality of rods thereby producing electricaldischarges in selected holes of said rods.
 9. The apparatus recited inclaim 7 in which one of said rods comprises the sealed fill tube forsaid envelope means.
 10. The apparatus recited in claim 1 in which saidcathode means comprises an electrically conductive cathode member havinga plurality of holes therein arranged in a predetermined pattern, andsaid anode means comprises a plurality of electrical conductors disposedadjacent said holes, respectively.
 11. The apparatus recited in claim 10further including a dielectric member sealed to said cathode memberthereby forming said envelope means.
 12. The apparatus recited in claim11 in which said dielectric member comprises a transparent member forviewing said cathode member, and said electrical conductors compriserespective electrically conductive strips disposed on the surface ofsaid transparent dielectric member internal to said envelope means. 13.The apparatus recited in claim 12 in which said strips are covered alongtheir respective surfaces with a dielectric material except at thoseportions thereof adjacent said holes.
 14. The apparatus recited in claim12 further including a source of positive electrical potentialsufficient to ignite electrical discharges through said ionizable gas,and addressing means coupling said connection means to said source ofelectrical potential for applying said positive potential to selectedones of said plurality of strips with respect to said conductive cathodemember thereby producing electrical discharges in selected holes of saidcathode member.
 15. The apparatus recited in claim 1 in which saidcathode means comprises a first dielectric member having a plurality ofholes arranged therein in a matrix of rows and columns, and a pluralityof electrically conductive hollow cathodes having respective hollowportions therein, said cathodes being disposed in said holes in saidfirst dielectric member respectively.
 16. The apparatus recited in claim15 in which said anode means comprises a plurality of first electricalconductors each disposed adjacent the hollow portions of a respectivecolumn of said cathodes, and said cathode means includes a plurality ofelEctrical row conductors each connecting the cathodes of a respectiverow.
 17. The apparatus recited in claim 16 further including a seconddielectric member sealed to said first dielectric member thereby formingsaid envelope means.
 18. The apparatus recited in claim 17 in which saidsecond dielectric member comprises a transparent member for viewing saidcathodes, and said first electrical conductors comprise respectiveelectrically conductive strips disposed on the surface of saidtransparent dielectric member internal to said envelope means.
 19. Theapparatus recited in claim 16 in which said cathodes comprise,respectively, electrically conductive rods having respective axial holesformed therein.
 20. The apparatus recited in claim 19 in which saidholes in said first dielectric member extend therethrough, said rods arehermetically sealed in said holes whereby portions thereof are exposedto the exterior of said envelope means, and said plurality of electricalrow conductors are connected to said exposed portions.
 21. The apparatusrecited in claim 19 further including means for applying a positivepotential to all of said first electrical conductors with respect to allof said row conductors sufficient to sustain electrical dischargesthrough said ionizable gas, means for increasing the potential at aselected one of said first electrical conductors and for decreasing thepotential at a selected one of said row conductors thereby producing apotential therebetween sufficient to ignite an electrical discharge inthe hole associated with the intersection of said selected conductors,and means for decreasing the potential at a selected one of said firstelectrical conductors and for increasing the potential at a selected oneof said row conductors thereby producing a potential therebetweensufficient to extinguish any electrical discharge sustained in the holeassociated with the intersection of said selected conductors.
 22. Theapparatus recited in claim 20 in which one of said rods comprises thesealed fill tube for said envelope means.
 23. The apparatus recited inclaim 1 in which said cathode means comprises a plurality ofelectrically conductive cathode members each having a row of holestherein, said rows being aligned to form columns of holes, and saidanode means comprises a plurality of first electrical conductors eachdisposed adjacent a respective column of said holes.
 24. The apparatusrecited in claim 23 in which said cathode members are sealed togetherwith electrical insulator means disposed therebetween.
 25. The apparatusrecited in claim 24 further including a dielectric member sealed to saidcathode members thereby forming said envelope means.
 26. The apparatusrecited in claim 25 in which said dielectric member comprises atransparent member for viewing said cathode members, and said firstelectrical conductors comprise respective electrically conductive stripsdisposed on the surface of said transparent member internal to saidenvelope means.
 27. The apparatus recited in claim 26 in which each saidcathode member includes a ridge between each pair of adjacent holesdisposed therein, said ridges and said electrical insulator meansextending to said surface of said transparent member internal to saidenvelope means thereby forming a barrier around each of said holes. 28.The apparatus recited in claim 26 further including means for applying apositive potential to all of said strips with respect to all of saidcathode members sufficient to sustain electrical discharges through saidionizable gas, means for increasing the potential at a selected one ofsaid strips and for decreasing the potential at a selected one of saidcathode members thereby producing a potential between said selectedstrip and said selected cathode member sufficient to ignite anelectrical discharge in the hole therein associated with said selectedstrip, and means for decreasing the potential at a selected one of saidstrips and for increasing the potential at a selected one of saidcathode members thereby producing a potential between said selectedstrip and said selected cathode member sufficient to extinguish anyelectrical discharge sustained in the hole therein associated with saidselected strip.
 29. Gas discharge display apparatus comprising firstcathode means having a plurality of first hollow cathode portionstherein having first and second openings thereinto respectively, firstanode means spaced from said first cathode means and disposed adjacentsaid first hollow portions, first gas-tight envelope means enclosingsaid first hollow portions and said first anode means with a firstionizable gas, said first envelope means including transparent portionsadjacent said first and second openings respectively, second cathodemeans having a plurality of second hollow cathode portions thereinhaving third and fourth openings thereinto respectively, second anodemeans spaced from said second cathode means and disposed adjacent saidsecond hollow portions, second gas-tight envelope means enclosing saidsecond hollow portions and said second anode means with a secondionizable gas, said second envelope means including transparent portionsadjacent said third and fourth openings respectively, and connectionmeans included in said cathode and anode means adapted for connection toa source of electrical potential to selectively apply suitablepotentials between said anode and cathode means to produce electricaldischarges in selected hollow cathode portions, said first and secondcathode means being disposed adjacent each other with said first andsecond hollow portions being aligned whereby light emanating from saidsecond and fourth openings enters said associated fourth and secondopenings respectively after transmission through said associatedtransparent portions disposed therebetween.
 30. A gas discharge displayelement comprising an electrically conductive hollow cathode having ahollow portion therein, an electrically conductive anode spaced fromsaid cathode and disposed adjacent said hollow portion, a transparentmember hermetically sealed to said cathode forming a gas-tight envelopeenclosing said hollow portion and said anode with an ionizable gas, andconnection means adapted for connection to a source of electricalpotential to selectively apply a suitable potential between said anodeand cathode to produce an electrical discharge in said hollow portion,said hollow portion having side wall surfaces providing the primaryelectron emitting surfaces thereof, said side wall surfaces having lowresistivity and said connecting means associated there-with providing ahigh conductance path from said side wall surfaces to said source ofpotential.
 31. The apparatus recited in claim 30 in which said anodecomprises a transparent electrically conductive film disposed on thesurface of said transparent member internal to said envelope.
 32. Theapparatus recited in claim 30 in which said potential comprises apositive potential at said anode with respect to said cathode sufficientto ignite electrical discharge through said ionizable gas.
 33. Theapparatus recited in claim 30 in which said anode is in such proximityto said hollow portion that only cathode glow discharges substantiallyconfined to said hollow portion may occur.